The present invention relates to a data transmission system which utilizes multiplex techniques to transmit data signals among interface circuits.
In the past, a variety of multiplexing systems have been used to reduce the wiring requirements in data transmission systems. Related U.S. patent application Ser. No. 567,476 and U.S. Pat. No. 4,293,947 both disclose data transmission systems in which the central station is connected to a series of remote stations by a bus which transmits both clock signals and data signals. Each of the remote stations includes a counter which maintains a count of the clock pulses. Each of the remote stations has a unique address, and when the count of clock pulses equals the address, the respective remote station is enabled so as to transmit data between the remote station and the central station via the bus.
This approach to a data transmission system requires the use of a relatively sophisticated central station that receives data signals from the remote stations, processes the data signals, and then sends out commands to the remote stations. With this approach, the remote stations do not transmit data directly from one remote station to another; instead the central station always acts as an intermediary.
In many applications the cost and complexity of such a sophisticated central station may be excessive. The present invention is directed to an improved data transmission system which allows one remote station to communicate directly with another, thereby eliminating the need for a sophisticated central station.